1. Technical Field
The present invention relates to a deterioration determination device for a vehicle-driving battery, and in particular, to technology of performing deterioration determination of the driving battery during running of a vehicle.
2. Related Art
Conventionally, for a vehicle which has a driving battery mounted therein and is adapted to be run by a motor, a method for determining a degree of deterioration (hereinafter, referred to as deterioration state) of the driving battery by calculating a resistance of the driving battery while the driving battery is charged by an external power supply has been established.
In this case, if the vehicle is an electric vehicle in where is run by driving the motor by an electric power supplied from the driving battery, charging must be performed by the external power supply, and therefore deterioration state of the driving battery can be determined by calculating a resistance of the driving battery during charging. However, in a case of a vehicle, such as PHEV, in which an engine and a driving battery are mounted therein and the driving battery can be charged by a regenerative brake during running, users could exist who charge the driving battery by power generation through driving of the engine and by the regenerative brake during running and hardly use charging by the external power supply. Therefore, when deterioration state of the driving battery is determined during charging by the external power supply, there is a possibility that depending upon use situations of the driving battery, a chance of calculating a resistance of the driving battery does not exist and thus it is difficult to grasp an exact deterioration state of the driving battery.
On the other hand, in the following Patent Document 1, a technique is known in which when input/output demands of an electric power to a driving battery based on operation state of a vehicle during running of the vehicle have preset input/output patterns, deterioration degree of the driving battery for each input/output pattern is diagnosed.
[Patent Document 1] Japanese Patent No. 4172222
However, unlike during charging by the external power supply, current values and voltage values detected during running are unstable, i.e., can be varied depending upon running state. Therefore, a resistance value of the driving battery calculated based on the current values and the voltage values detected during running is also likely to be varied. In addition, if variations in the resistance value are occurred, there is a risk that deterioration state of the driving battery cannot be exactly grasped and thus deterioration state of the driving battery can be erroneously determined.
To this end, an object of the present invention is to provide a deterioration determination device for a vehicle-driving battery, which makes it possible to grasp deterioration state of the driving battery at a high accuracy even during running.